1. Field of the Invention
This invention relates in general to mobile radio telephone communication systems, and more specifically, to rapid system access end registration for mobile phones when the mobile phone operates in an area outside of its home service area.
2. Description of Related Art
Mobile phones, which include cellular phones, personal communications systems (PCS) phones, enhanced specialized mobile radio (ESMR) phones, and other radio telephone technologies, combine the mobility of the radio link and the world-wide land telephone network to provide a mobile communications link to any telephone in the world. As mobile phones have become more prevalent throughout the world, the number of system operators have increased.
A service provider or system operator, such as the assignee AirTouch Communications, Inc. and others, may operate mobile phone systems in different markets using different frequency bands (e.g., different portions of the allocated spectrum) and different types of systems (e.g., FDMA, TDMA, CDMA, PCS, GSM, etc.). When a mobile phone roams outside of its home service area, it is desirable that its calls use a preferred system, e.g., one operated by the same service provider as its home service area or one operated by another service provider having some relationship with the service provider of its home service area. However, the preferred system may be operating within the foreign service area on a different frequency band than the home service area. As a result, the mobile phone must also identify a frequency band and system type associated with a preferred system in a foreign service area to use for its communications.
Generally, a mobile phone identifies a preferred system by scanning for one or more System IDs (SIDs) and/or Group IDs (GIDs) and/or Network IDs (NIDs) associated with one or more preferred service providers. The SID is a binary identification value uniquely assigned to a mobile phone system, the GID is a subset of the most significant bits of the SID that are used to identify a group of mobile phone systems, e.g., those mobile phone systems operated by AirTouch Communications, Inc., the assignee of the present invention, or other service providers, and the NID indicates the location within that Major Trading Area (MTA) serviced by the mobile phone system. The SID, GID, and/or NID are typically embedded within control data transmitted by the mobile phone system.
In a roaming situation outside the mobile phone's home service area, the mobile phone may have to scan a large number of frequency bands in order to identify a preferred system. For example, according to the presently allocated spectrum, the mobile phone may have to scan: 1) Cellular Band A; 2) Cellular Band B; 3) PCS Band A; 4) PCS Band B; 5) PCS Band C; 6) PCS Band D; 7) PCS Band E; and 8) PCS Band F. Of course, those skilled in the art will recognize that, in the future, the mobile phone may have to also scan other allocated spectrums.
In addition, beginning in 1996, the FCC has allowed current license holders of particular frequency bands to sell or lease sub-bands to other service providers. Thus, in a roaming situation outside the mobile phone's home service area, the mobile phone may also have to scan a large number of sub-bands as well.
As a result, it is difficult and time-consuming for a roaming mobile phone to locate a preferred system due to the large number of possible frequency bands, sub-bands, and possible setup channels that may have to be scanned by the mobile phone. Indeed, users may not have the patience to wait for this scanning process to complete. Thus, there is a need in the art for methods of rapid system access and registration for roaming mobile phones.